Long-simmering resentment has blossomed into a full-on feud between two members of the 1980s literary Brat Pack — Tama Janowitz and Jay McInerney.

Janowitz, who wrote “Slaves of New York,” calls McInerney, author of “Bright Lights, Big City,” an “idiot” in the Guardian.

“I remember being so, so upset because Jay McInerney was interviewed, and he said how terrible it was that an author does an ad: ‘Tama Janowitz did ads, an author who does ads is a whore,’ ” Janowitz said.

Asked if she had ever confronted McInerney, she replied, “No, it’s ridiculous to argue with idiots.”

McInerney told me he doesn’t remember ever calling Janowitz names. “I remember writing a review of ‘Slaves of New York’ for the New York Times Book Review, which put her on the map,” McInerney said. “Was I being idiotic when I praised her book?”

Janowitz, who has done ads for Disaronno and Apple, pointed out that Ernest Hemingway, John Steinbeck and Joan Didion all appeared in ads. But McInerney said that doesn’t make it right.

“That’s the way I feel. As a fiction writer, you need your credibility,” McInerney said.

“John Cheever did a Rolex ad, and I remember being bummed out. Like, why would he do that?”